Grease composition for precision equipment and timepiece containing the same

ABSTRACT

A grease composition for a precision instrument comprising a lithium soap grease or a urea grease, and an anti-wear agent, wherein the lithium soap grease and the urea grease are each a grease having no hydroxyl group in a molecule, and the anti-wear agent is contained in an amount of 0.1 to 20% by weight based on the total amount of the grease composition. By the use of the grease composition for a sliding mechanism of a precision instrument such as a watch, an appropriate slip torque can be obtained, and the precision instrument such as a watch can operate stably.

FIELD OF THE INVENTION

The present invention relates to a grease composition for a precisioninstrument and a watch using the same. More particularly, the inventionrelates to a grease composition used for a slide portion of a precisioninstrument such as a watch, e.g., a sliding mechanism of a second wheeland pinion of a watch part, and a watch in which the grease compositionis used.

BACKGROUND OF THE INVENTION

As watches, there are two types of mechanical watches which operate bythe use of power of a mainspring and electronic watches which operate byelectric power of battery loaded therein. Each of the electronic watchesand the mechanical watches has a train wheel portion to move hour hand,minute hand and second hand, such as wheels and bridges, and a slideportion such as levers. For the train wheel portion and the slideportion, parts made of metals or plastics are used taking processabilityand strength into account.

For the operation of the hands of watches, a magnetized rotor rotates180° for one second and this rotation is transmitted in the followingmanner. That is to say, the rotation of the rotor is transmitted to afifth wheel and pinion, a fourth wheel and pinion, a third wheel andpinion, a second wheel and pinion, a minute wheel, and an hour wheel inthis order, and the fourth wheel and pinion moves the second hand, thesecond wheel and pinion moves the minute hand, and the hour wheel movesthe hour hand, whereby each hand is operated.

Watches usually have a time-adjusting function. When a crown is pulledin order to adjust time, a clutch wheel is gears into the minute wheel.When the crown is revolved in this state, the clutch wheel is rotated tothereby rotate the minute wheel. By the rotation of the minute wheel,the hour wheel is rotated, whereby the hour hand can be moved. By therotation of the minute wheel, the second wheel and pinion is alsorotated, whereby the minute hand can be moved.

The minute wheel, however, is interlocked with the rotor through thesecond wheel and pinion, the third wheel and pinion, the fourth wheeland pinion, and the fifth wheel and pinion, so that if the crown isrevolved, even the rotor is rotated. Then, in order to prevent rotationof the rotor caused by adjusting time, watches are equipped with abraking mechanism and a sliding mechanism to rotate only wheelsnecessary to adjust time. The sliding mechanism is usually set on thesecond wheel and pinion.

The sliding mechanism has an appropriate torque (referred to as “sliptorque”), and when a force higher than a certain torque is applied, thesliding mechanism is activated, and thereby, rotation is not transmittedbetween the second wheel and pinion, and the third wheel and pinion.More specifically, in the usual motion of hands, the rotation istransmitted from the third wheel and pinion to the second wheel andpinion, but when the crown is revolved, a force of a certain torque isapplied to actuate the sliding mechanism, whereby rotation is nottransmitted from the second wheel and pinion to the third wheel andpinion.

However, if the time-adjusting operation is repeatedly carried out, thesliding mechanism suffers frictional wear and is deteriorated to therebylower the slip torque. Consequently, it becomes difficult to stop thehand at the desired position in the time-adjusting operation, or also inthe usual motion, the sliding mechanism sometimes is activated tothereby stop the motion of the minute hand.

Therefore, a lithium soap grease containing as a base oil an ester typesynthetic oil or a mineral oil is conventionally poured into the slidingmechanism to prevent deterioration of the sliding mechanism caused byfrictional wear and thereby inhibit lowering of torque. However, if asynthetic oil having a large total acid number and exhibiting metalcorrosiveness (e.g., Mabis 9415) is used for a metal part of a precisioninstrument such as a watch, the metal part is occasionally tarnished ordissolved. Further, if a grease (e.g., CH-1 available from Citizen WatchCo., Ltd.) having poorer storage stability than a high-purity syntheticbase oil (e.g., International Publication No. WO01/59043) is used, thereis brought about a problem that the sliding mechanism is immediatelydeteriorated. On this account, development of grease having a smalltotal acid number and exhibiting excellent storage stability has beendesired.

Furthermore, grease having been poured into the sliding mechanismsometimes mingles with a lubricating oil that has been applied in orderto slide the second wheel and pinion. As a result, deterioration of theslide portion or change of properties of the lubricating oil sometimesoccurs. For example, if the aforesaid Mabis 9415 is mixed with thelubricating oil, metal corrosiveness of the lubricating oil is increasedto sometimes deteriorate the slide portion. If the CH-1 available fromCitizen Watch Co., Ltd. is mixed with the lubricating oil, change ofproperties of the lubricating oil takes place and the propertiesinherent in the lubricating oil cannot be obtained in some cases.

Then, as a sliding mechanism having an appropriate torque, a secondwheel and pinion manufactured in combination with a resin has beenproposed (Japanese Patent Publication No. 16705/1996, Japanese PatentLaid-Open Publication No. 123783/1994, Japanese Patent Laid-OpenPublication No. 196747/1993). This second wheel and pinion is employablewithout oil-feeding and is prevented from mixing of a lubricating oil,but it is difficult to easily manufacture the second wheel and pinionbecause of its complicated structure. Moreover, there is another problemthat the sliding mechanism has poor wear resistance because it is madeof a resin.

Other various grease compositions have been heretofore proposed (e.g.,Japanese Patent Laid-Open Publication No. 31706/1978, Japanese PatentLaid-Open Publication No. 35963/1999, Japanese Patent Laid-OpenPublication No. 336760/1999, Japanese Patent Laid-Open Publication No.336761/1999, Japanese Patent Laid-Open Publication No. 172656/2001,Japanese Patent Laid-open Publication No. 308125/2002), but these greasecompositions are intended for large-sized machines, and theirconsistency is large. Therefore, even if these grease compositions areused for sliding mechanism of watches, it is difficult that the slidingmechanism has a suitable torque.

OBJECT OF THE INVENTION

It is an object of the present invention to provide a grease compositionfor a precision instrument which has no metal corrosiveness, hardlysuffers change of properties and can maintain an appropriate slip torquein a precision instrument such as a watch. It is another object of theinvention to provide a watch which exhibits stable operating performanceby the use of the grease composition for its sliding mechanism..

DISCLOSURE OF THE INVENTION

The present inventor has earnestly studied to solve the above problems,and as a result, he has found that a grease composition for a precisioninstrument containing grease having no hydroxyl group in a molecule doesnot have metal corrosiveness and hardly suffers change of properties.Based on the finding, the present invention has been accomplished.

That is to say, a grease composition for a precision instrumentaccording to the invention is a grease composition for a precisioninstrument comprising a lithium soap grease or a urea grease, and ananti-wear agent, wherein the lithium soap grease and the urea grease areeach grease having no hydroxyl group in a molecule, and the anti-wearagent is contained in an amount of 0.1 to 20% by weight based on thetotal amount of the grease composition.

The lithium soap grease or the urea grease is preferably obtained from apolyol ester oil having no hydroxyl group in a molecule, a paraffinichydrocarbon oil comprising an α-olefin polymer of 30 or more carbonatoms, or an ether oil having no hydroxyl group in a molecule.

The ether oil is preferably an ether oil represented by the followingformula (1):

wherein R₁ and R₃ are each independently an alkyl group of 1 to 18carbon atoms or a monovalent aromatic hydrocarbon group of 6 to 18carbon atoms, R₂ is an alkylene group of 1 to 18 carbon atoms or adivalent aromatic hydrocarbon group of 6 to 18 carbon atoms, and n is aninteger of 1 to 5.

The anti-wear agent is preferably at least one compound selected from aneutral phosphate, a neutral phosphite and calcium borate.

The grease composition for a precision instrument of the inventionpreferably further comprises a solid lubricant in an amount of 0.01 to5% by weight based on the total amount of the grease composition, andthe solid lubricant preferably comprises molybdenum disulfide and/orPTFE particles.

The grease composition for a precision instrument of the inventionpreferably further comprises a metal deactivator, and the metaldeactivator is preferably benzotriazole and/or a derivative thereof.

The grease composition for a precision instrument of the inventionpreferably further comprises an antioxidant, and the antioxidant ispreferably a phenol type antioxidant and/or an amine type antioxidant.The phenol type antioxidant is preferably 2,6-di-tributyl-p-cresol,2,4,6-tri-t-butylphenol or 4,4′-methylenebis(2,6-di-tributylphenol), andthe amine type antioxidant is preferably a diphenylamine derivative.

The lithium soap grease or urea grease, which is contained in the greasecomposition for a precision instrument of the invention, preferably hasa change in weight of not more than 10% by weight after the grease isheld at 90° C. for 1000 hours. The grease composition for a precisioninstrument preferably has a total acid number of not more than 0.2mgKOH/g.

A watch according to the invention is a watch in which theabove-mentioned grease composition for a precision instrument is usedfor a sliding mechanism of its slide portion.

When the watch of the invention is a watch wherein a grease compositionfor a precision instrument is used for a sliding mechanism of a slideportion and a lubricating oil composition is used for portions otherthan the sliding mechanism of the slide portion, a combination of thegrease composition for a precision instrument and the lubricating oil ispreferably any one of the following combinations:

(1) the grease composition for a precision instrument is a greasecomposition obtained from a polyol ester oil having no hydroxyl group ina molecule, and the lubricating oil composition is a lubricating oilcomposition obtained from the polyol ester oil having no hydroxyl groupin a molecule;

(2) the grease composition for a precision instrument is a greasecomposition obtained from a paraffinic hydrocarbon oil comprising anα-olefin polymer of 30 or more carbon atoms, and the lubricating oilcomposition is a lubricating oil composition obtained from theparaffinic hydrocarbon oil comprising an α-olefin polymer of 30 or morecarbon atoms; and

(3) the grease composition for a precision instrument is a greasecomposition obtained from an ether oil having no hydroxyl group in amolecule, and the lubricating oil composition is a lubricating oilcomposition obtained from the ether oil having no hydroxyl group in amolecule.

A maintenance method of a watch according to the invention is amaintenance method of a watch in which a grease composition for aprecision instrument containing a solid lubricant is used for a slidingmechanism of a slide portion, comprising:

-   -   after disassembly and washing of the watch, re-assembling the        watch using a grease composition for a precision instrument        containing no solid lubricant in a sliding mechanism of a slide        portion.

PREFERRED EMBODIMENTS OF THE INVENTION

<Grease Composition for Precision Instrument>

A grease composition for a precision instrument according to theinvention contains (A) a lithium soap grease or a urea grease, (B) ananti-wear agent, and if necessary, (C) a solid lubricant, (D) a metaldeactivator and (E) an antioxidant. (A) Grease

The grease for use in the invention is a lithium soap grease or a ureagrease having no hydroxyl group in a molecule. Such grease can beprepared by the use of (a1) a polyol ester oil having no hydroxyl groupin a molecule, (a2) a paraffinic hydrocarbon oil, or (a3) an ether oilhaving no hydroxyl group in a molecule.

(a1) Polyol Ester Oil having No Hydroxyl Group in Molecule

The polyol ester oil having no hydroxyl group in a molecule (referred toas a “polyol ester oil (a1)” simply hereinafter) for use in theinvention can be prepared by reacting a polyol having at least twohydroxyl groups in one molecule with a monovalent acid or its salt in amixing molar ratio ((monovalent acid or its salt)/polyol) of not lessthan 1. The resulting polyol ester oil (a1) is a complete ester havingno hydroxyl group in a molecule.

Examples of polyols having at least two hydroxyl groups in one moleculefor use in the invention include neopentyl glycol, trimethylolpropane,pentaerythritol and dipentaerythritol.

Examples of the monovalent acids include:

-   -   saturated aliphatic monocarboxylic acids, such as acetic acid,        propionic acid, butyric acid, isobutyric acid, valeric acid,        pivalic acid, heptanoic acid, octanoic acid, nonanoic acid,        decanoic acid, lauric acid, myristic acid and palmitic acid;

unsaturated aliphatic monocarboxylic acids, such as stearic acid,acrylic acid, crotonic acid and oleic acid; and

-   -   cyclic carboxylic acids, such as benzoic acid, toluic acid,        naphthoic acid, cinnamic acid, cyclohexanecarboxylic acid,        nicotinic acid, isonicotinic acid, 2-furancarboxylic acid,        pyrrol-N-carboxylic acid, monoethyl malonate and ethyl        hydrogenphthalate.

Examples of the salts of monovalent acids include chlorides of theabove-mentioned monovalent acids.

Examples of the polyol ester oils (a1) include neopentyl glycol-decanoicacid/octanoic acid mixed ester, trimethylolpropnane-valericacid/heptanoic acid mixed ester, trimethylolpropane-decanoicacid/octanoic acid mixed ester, trimethylolpropane nonanoate, andpentaerythritol-heptanoic acid/decanoic acid mixed ester.

(a2) Paraffinic Hydrocarbon Oil

The paraffinic hydrocarbon oil (a2) for use in the invention isdesirably an α-olefin polymer of 30 or more carbon atoms, preferably 30to 50 carbon atoms. The α-olefin polymer is preferably a homopolymer ofone monomer selected from ethylene and an α-olefin of 3 to 18 carbonatoms, preferably an α-olefin of 10 to 18 carbon atoms, or a copolymerof at least two monomers selected from ethylene and α-olefins of 3 to 18carbon atoms, preferably an α-olefin of 10 to 18 carbon atoms. Examplesof such polymers include a trimer of 1-decene, a trimer of 1-undecene, atrimer of 1-dodecene, a trimer of 1-tridecene, a trimer of1-tetradecene, and a copolymer of 1-hexene and 1-pentene.

(a3) Ether Oil having No Hydroxyl Group in Molecule

The ether oil having no hydroxyl group in a molecule (referred to as an“ether oil (a3)” simply hereinafter) for use in the invention is notspecifically restricted provided that the ether oil has no hydroxylgroup in its molecule, but preferable is an ether oil represented by thefollowing formula (1):

wherein R₁ and R₃ are each independently an alkyl group of 1 to 18carbon atoms or a monovalent aromatic hydrocarbon group of 6 to 18carbon atoms, R₂ is an alkylene group of 1 to 18 carbon atoms or adivalent aromatic hydrocarbon group of 6 to 18 carbon atoms, and n is aninteger of 1 to 5.

Examples of the alkyl groups of 1 to 18 carbon atoms include methyl,ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,n-pentyl, isopentyl, tert-pentyl, neopentyl, hexyl, isohexyl, heptyl,octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl,hexadecyl, heptadecyl and octadecyl.

Examples of the monovalent aromatic hydrocarbon groups of 6 to 18 carbonatoms include phenyl, tolyl, xylyl, benzyl, phenethyl, 1-phenylethyl and1-methyl-1-phenylethyl.

Examples of the alkylene. groups of 1 to 18 carbon atoms includemethylene, ethylene, propylene and butylene.

Examples of the divalent aromatic hydrocarbon groups of 6 to 18 carbonatoms include phenylene and 1,2-naphthylene.

(Grease (A))

The grease (A) for use in the invention is a lithium soap grease or aurea grease of (a1) the polyol ester oil having no hydroxyl group in amolecule, (a2) the paraffinic hydrocarbon oil or (a3) the ether oilhaving no hydroxyl group in a molecule.

The lithium soap grease can be prepared by a publicly known processusing the polyol ester oil (a1), the paraffinic hydrocarbon oil (a2) orthe ether oil (a3). For example, the lithium soap grease can be preparedby adding lithium stearate to the polyol ester oil (a1), the paraffinichydrocarbon oil (a2) or the ether oil (a3) and heating them at themelting point of lithium stearate or above.

The urea grease can be prepared by a publicly known process using thepolyol ester oil (a1), the paraffinic hydrocarbon oil (a2) or the etheroil (a3). For example, the urea grease can be prepared by adding adiurea compound represented by the following formula (2) to the polyolester oil (a1), the paraffinic hydrocarbon oil (a2) or the ether oil(a3) and heating them at the melting point of the diurea compound orabove.R₄—HNCONH—R₅—HNCONH—R₆  (2)wherein R₄ and R₆ are each independently a hydrocarbon group of 1 to 10carbon atoms, and R₅ is a hydrocarbon group of 6 to 15 carbon atoms.

Examples of the R₄ and R₆ include alkyl groups of 1 to 10 carbon atoms.Of these, butyl, pentyl, hexyl and heptyl are preferred.

Examples of the R₅ include groups represented by the following formula:

Of these, the groups represented by:

are preferred.

The grease (A) for use in the invention is grease used for a precisioninstrument such as a watch. The grease (A) has a penetration of ¼-cone(defined by JIS K2220) at 25° C. of a specific range. Herein, thepenetration of ¼-cone (JIS K2220) is a depth which ¼-cone (JIS K2220)penetrates into grease at a specified temperature for specified time, asmeasured by the following manner.

(Measurement Method of Penetration (25° C.) of ¼-cone (JIS K2220))

The penetration (25° C.) of ¼-cone (JIS K2220) is measured by the use ofthe consistometer and ¼-cone (total amount of a holding bar and thecone: 9.38 g) as described in JIS K2220. A measured sample is preparedin accordance with the method for preparing a sample as described in the¼-worked penetration measurement method defined.by JIS K2220 in order tohomogenize grease, and the temperature of the sample is kept at 25° C. Apot wherein the sample kept at 25° C. is placed is put on the stage ofthe consistometer, and then a tip of the ¼-cone is brought in contactwith the center of a sample surface. Thereafter, the ¼-cone is allowedto penetrate into the sample for specified time (0.1 seconds or 1second). A reading of indicating gauge at the time is read, and isregarded as a penetration (25° C., unit: mm) of ¼-cone (JIS K2220) forspecified time (0.1 seconds or 1 second).

The ¼-cone penetration of the grease (A) can be controlled by mixing, atan appropriate ratio, the polyol ester oil (a1) having no hydroxyl groupin a molecule, the paraffinic hydrocarbon oil (a2) or the ether oil (a3)having no hydroxyl group in a molecule with the lithium soap grease orurea grease prepared by the method described above.

The grease (A) for use in the invention has a penetration (25° C.) of¼-cone (JIS K2220) for 1 second of not less than 5.0 mm, preferably notless than 5.5 mm. Particularly, when the grease composition for aprecision instrument of the invention is used for a sliding mechanism,the grease (A) has desirably a penetration (25° C.) of ¼-cone (JISK2220) for 0.1 seconds of 10.0 to 25.0 mm, preferably 12.0 to 22.0 mm,still preferably 13.0 to 18.0 mm. Further, when the grease compositionfor a precision instrument of the invention is used for an automatic ofa mechanical watch, the grease (A) has desirably a penetration (25° C.)of ¼-cone (JIS K2220) for 1 second of 5.0 to 7.0 mm, preferably 5.7 to6.7 mm.

When the ¼-cone penetration of the grease (A) is in the above range, thesliding mechanism has a suitable torque, and a precision instrument suchas a watch can be stably operated.

The grease (A) for use in the invention has no hydroxyl group in amolecule, and does not absorb moisture or very hardly absorbs moisture.Therefore, a grease composition for a precision instrument containingthe grease (A) is free from change of properties and does not exhibitmetal corrosiveness. Hence, corrosion of a slide portion of a precisioninstrument such as a watch is not brought about, and the precisioninstrument such as a watch can be stably operated. The greasecomposition for a precision instrument of the invention has a percentageof moisture absorption of usually not more than 1.0% by weight,preferably not more than 0.5% by weight.

In the grease composition for a precision instrument of the invention,the grease (A) is contained in an amount of 80 to 99.8% by weight,preferably 90 to 99% by weight, more preferably 93 to 97% by weight,based on the total amount of the grease composition.

(B) Anti-wear Agent

The anti-wear agent (B) for use in the invention is, for example, ametal type anti-wear agent, a sulfide type anti-wear agent, an acidphosphate type anti-wear agent, an acid phosphite type anti-wear agent,an acid phosphoric ester amine salt, a neutral phosphate type anti-wearagent, a neutral phosphite type anti-wear agent or calcium borate.

Examples of the metal type anti-wear agents includealkyldithiophosphoric acid metal salts, such as zincdiethyldithiophosphate (ZnDTP) and molybdenum diethyldithiophosphate(MoDTP).

Examples of the sulfide type anti-wear agents include alkyl sulfides,such as distearyl sulfide.

Examples of the acid phosphate type anti-wear agents include acidphosphates, such as lauryl acid phosphate.

Examples of the acid phosphite type anti-wear agents include acidphosphites, such as dilauryl hydrogenphosphite.

Examples of the acid phosphoric ester amine salts include lauryl acidphosphate diethylamine salt.

Examples of the neutral phosphate type anti-wear agents include neutralphosphates, such as triethyl phosphate, trioctyl phosphate,tris(tridecyl) phosphate, tristearyl phosphate, trimethylolpropanephosphate, triphenyl phosphate, tricresyl phosphate, trixylenylphosphate, tris(nonylphenyl) phosphate, tris(2,4-di-t-butylphenyl)phosphate, tetraphenyldipropylene glycol diphosphate,tetraphenyltetra(tridecyl) pentaerythritol tetraphosphate,tetra(tridecyl)-4,4′-isopropylidenediphenyl diphosphate, bis(tridecyl)pentaerythritol diphosphate, bis(nonylphenyl) pentaerythritoldiphosphate, distearyl pentaerythritol diphosphate and hydrogenatedbisphenol A pentaerythritol phosphate polymer.

Examples of the neutral phosphite type anti-wear agents include neutralphosphites, such as triethyl phosphite, trioctyl phosphite,tris(tridecyl) phosphite, trioleyl phosphite, tristearyl phosphite,trimethylolpropane phosphite, triphenyl phosphite, tris(nonylphenyl)phosphite, tris(2,4-di-t-butylphenyl) phosphite, tetraphenyldipropyleneglycol diphosphite, tetraphenyltetra(tridecyl) pentaerythritoltetraphosphite, tetra(tridecyl)-4,4′-isopropylidenediphenyl diphosphite,bis(tridecyl) pentaerythritol diphosphite, bis(nonylphenyl)pentaerythritol diphosphite, distearyl pentaerythritol diphosphite andhydrogenated bisphenol A pentaerythritol phosphite polymer.

The above anti-wear agents can be used singly or in combination of twoor more kinds.

Of the above anti-wear agents, preferable are a neutral phosphate, aneutral phosphite and calcium borate. By the use of a neutral phosphate,a neutral phosphite or calcium borate, for a longer period of time,metal corrosion of a slide portion of a precision instrument such as awatch is not brought about, frictional wear of the slide portion can beprevented, and the precision instrument such as a watch can be stablyoperated.

In the grease composition for a precision instrument of the invention,the anti-wear agent (B) is contained in an amount of 0.1 to 20% byweight, preferably 1 to 10% by weight, more preferably 3 to 7% byweight, based on the total amount of the grease composition. When theanti-wear agent (B) is added in the above amount, frictional wear of aslide portion of a precision instrument such as a watch can be favorablyprevented, and the precision instrument such as a watch can be stablyoperated.

(C) Solid Lubricant

Examples of the solid lubricants (C) for use in the invention includemolybdenum disulfide and PTFE particles. The PTFE particles arepreferably those having a primary particle diameter of 0.5 to 8 μm.

The above solid lubricants can be used singly or in combination of twoor more kinds.

In the grease composition for a precision instrument of the invention,the solid lubricant (C) is desirably contained in an amount of 0.01 to5% by weight, preferably 0.01 to 3% by weight, more preferably 0.3 to 1%by weight, based on the total amount of the grease composition. When thesolid lubricant (C) is added in the above amount, frictional wear of aslide portion of a precision instrument such as a watch can be favorablyprevented even if a part for the precision instrument has highextreme-pressure properties, and the precision instrument such as awatch can be stably operated.

(D) Metal Deactivator

The metal deactivator (D) for use in the invention is preferablybenzotriazole or its derivative.

Examples of the benzotriazole derivatives include2-(2′-hydroxy-5′-methylphenyl)benzotriazole,2-[2′-hydroxy-3′,5′-bis(α,α-dimethylbenzyl)phenyl]benzotriazole,2-(2′-hydroxy-3′,5′-di-t-butylphenyl)benzotriazole, compoundsrepresented by the following formula (3), such as1-(N,N-bis(2-ethylhexyl)aminomethyl)benzotriazole, and compoundsrepresented by the following formula (4),

wherein R₇, R₈ and R₉ are each independently an alkyl group of 1 to 18carbon atoms.

wherein R₁₀ is an alkyl group of 1 to 18 carbon atoms.

The above metal deactivators can be used singly or in combination of twoor more kinds.

In the grease composition for a precision instrument of the invention,the metal deactivator (D) is desirably contained in an amount of 0.01 to3% by weight, preferably 0.02 to 1% by weight, more preferably 0.03 to0.06% by weight, based on the total amount of the grease composition.When the metal deactivator (D) is added in the above amount, corrosionof a metal such as copper can be favorably prevented.

(E) Antioxidant

The antioxidant (E) for use in the invention is preferably a phenol typeantioxidant or an amine type antioxidant.

Examples of the phenol type antioxidants include2,6-di-1-butyl-p-cresol, 2,4,6-tri-t-butylphenol and4,4′-methylenebis(2,6-di-t-butylphenol).

Examples of the amine type antioxidants include diphenylaminederivatives.

The above antioxidants can be used singly or in combination or two ormore kinds.

In the grease composition for a precision instrument of the invention,the antioxidant (E) is desirably contained in an amount of 0.01 to 3% byweight, preferably 0.01 to 2% by weight, more preferably 0.03 to 1.2% byweight, based on the total amount of the grease composition. When theantioxidant (E) is added in the above amount, change of properties ofthe grease composition and corrosion of a slide portion of a precisioninstrument such as a watch can be prevented over a long period of time.

<Grease Composition for Precision Instrument>

The grease composition for a precision instrument according to theinvention contains (A) the lithium soap grease or the urea grease and(B) the anti-wear agent. When a sliding mechanism of a precisioninstrument such as a watch is assembled by the use of such a greasecomposition, a decrease ratio of the slip torque after a 10-yearsaccelerated test can be lowered to not more than 15%. Herein, thedecrease ratio of a slip torque (referred to as “torque decrease ratio”hereinafter) is defined as change (change ratio) of a slip torque afterthe 10-years accelerated test for adjusting time to that at the start ofoperation test for sliding mechanism.

The grease composition for a precision instrument of the inventionfurther contains, if necessary, the solid lubricant (C). When a slidingmechanism of a precision instrument such as a watch is assembled by theuse of such a grease composition, a decrease ratio of the slip torquecan be lowered to not more than 9%. Further, when the grease compositionfor a precision instrument of the invention contains the metaldeactivator (D) and the antioxidant (E), a decrease ratio of the sliptorque at high temperature can be lowered to not more than 10%.

In the grease composition for a precision instrument of the invention,the change in weight (also referred to as “evaporation loss”) of thelithium soap grease or urea grease , measured after the grease is heldat 90° C. for 1000 hours, is desirably not more than 10% by weight,preferably not more than 5% by weight, more preferably not more than 1%by weight, particularly preferably not more than 0.5% by weight. Whenthe change in weight of the grease, measured after the grease is held at90° C. for 1000 hours, is not more than 10% by weight, a precisioninstrument using the grease composition containing such grease, such asa watch, exhibits excellent high-temperature operating stability.

The total acid number of the grease composition is desirably not morethan 0.2 mgKOH/g. When the total acid number of the grease compositionis not more than 0.2 mgKOH/g, corrosion of parts of a precisioninstrument such as a watch can be prevented.

<Watch>A watch according to the invention is a watch in which theabove-mentioned grease composition for a precision instrument is used inthe slide portion. For example, the grease composition for a precisioninstrument is applied to a slip portion of a second wheel and pinionhaving a sliding mechanism. In the watch in which the grease compositionfor a precision instrument is used for a sliding mechanism, frictionalwear of part(s) of the sliding mechanism can be inhibited, and the watchexhibits stable operating performance. Particularly in a watch whereinthe grease composition for a precision instrument containing, as theanti-wear agent, a neutral phosphate, a neutral phosphite or calciumborate is used, frictional wear of part(s) of the sliding mechanism canbe inhibited and the watch operates stably, over a long period of time.

When the grease composition for a precision instrument of the inventionis used for a sliding mechanism of a slide portion of a watch and thelubricating oil composition is used for portions other than the slidingmechanism, preferred combinations of the grease composition and thelubricating oil composition are the following combinations (1) to (3).

(1) Grease composition: grease composition obtained from the polyolester oil (a1)

-   -   Lubricating oil composition: lubricating oil composition        obtained from the polyol ester oil (a1)    -   (2) Grease composition: grease composition obtained from the        paraffinic hydrocarbon oil (a2)    -   Lubricating oil composition: lubricating oil composition        obtained from the paraffinic hydrocarbon oil (a2)    -   (3) Grease composition: grease composition obtained from the        ether oil (a3)    -   Lubricating oil composition: lubricating oil composition        obtained from the ether oil (a3)

The lubricating oil composition used in the invention is notspecifically restricted provided that the lubricating oil composition isa lubricating oil composition used for a watch and that the abovecombinations are satisfied.

By the use of the above combinations of the grease composition for aprecision instrument and the lubricating oil composition in a watch,properties of the lubricating oil are not changed even when they aremixed with each other, and the watch can continuously operate morestably.

<Maintenance Method of Watch>

A maintenance method of a watch according to the invention is amaintenance method of a watch in which the grease composition for aprecision instrument containing a solid lubricant is used for a slidingmechanism of a slide portion.

First, the watch assembled using the grease composition for a precisioninstrument containing a solid lubricant is disassembled and washed.Thereafter, when this watch is re-assembled, the grease composition fora precision instrument containing no solid lubricant is used for asliding mechanism of a slide portion.

Even if the grease composition for a precision instrument containing nosolid lubricant is used, a slip torque does not extremely decrease. Evenafter disassembly and washing, stable operating performance of the watchis obtained.

The grease composition for a precision instrument containing no solidlubricant is cheaper than the grease composition for a precisioninstrument containing a solid lubricant, so that the maintenance methodof a watch of the invention is economically excellent.

EXAMPLES

<Measurement Method of Penetration (25° C.) of ¼-cone (JIS K2220) forGrease (A)>

The penetration (25° C.) of ¼-cone (JIS K2220) for the grease (A) for aspecified time (0.1 seconds or 1 second) was measured by the use of theconsistometer and ¼-cone (total amount of a holding bar and the cone:9.38 g) as described in JIS K2220. In accordance with JIS K2220, thegrease (A) was placed into a ¼-mixing pot, and the temperature of thegrease (A) was maintained at 25° C. The grease (A) was sufficientlymixed to obtain a homogeneous sample. The pot in which the sample wasplaced was put on the stage of the consistometer, and then a tip of the¼-cone was brought in contact with the center of a sample surface.Thereafter, a agrafe was pushed to penetrate the ¼-cone into the samplefor specified time (0.1 seconds or 1 second). A reading of indicatinggauge at the time was read, and was regarded as a penetration (25° C.,unit: mm) of ¼-cone (JIS K2220) for the specified time.

<Preparation of Grease (A1)>

Greases (A1) used in Examples 1 to 6 and Comparative Examples 1 to 2 aregiven below.

(Lithium Soap Grease (A1-1))

Trimethylolpropane and valeric acid were mixed in a mixing ratio of 1:4(trimethylolpropane:valeric acid) by mol to perform esterificationreaction, whereby a crude trimethylolpropane-valeric acid ester wasobtained. From the crude trimethylolpropane-valeric acid ester, atrimethylolpropane-valeric acid ester (a1-1) having no hydroxyl group ina molecule was separated by the use of Wakogel (available from Wako PureChemical Ind., Ltd.). By the measurement of an infrared absorptionspectrum of the trimethylolpropane-valeric acid ester (a1-1), it wasconfirmed that no hydroxyl group was present in a molecule.

To the trimethylolpropane-valeric acid ester (a1-1), lithium stearatewas added in an amount of not less than 10% by weight, and they wereheated to not lower than the melting point of lithium stearate to obtaina lithium soap grease. Then, to the lithium soap grease, thetrimethylolpropane-valeric acid ester (a1-1) was further added so thatthe penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 15.2mm, to prepare a lithium soap grease (A1-1).

(Lithium Soap Grease (A1-2))

Trimethylolpropane and nonanoic acid were mixed in a mixing ratio of 1:4(trimethylolpropane:nonanoic acid) by mol to perform esterificationreaction, whereby a crude trimethylolpropane-nonanoic acid ester wasobtained. From the crude trimethylolpropane-nonanoic acid ester, atrimethylolpropane-nonanoic acid ester (a1-2) having no hydroxyl groupin a molecule was separated by the use of Wakogel (available from WakoPure Chemical Ind., Ltd.). By the measurement of an infrared absorptionspectrum of the trimethylolpropane-nonanoic acid ester (a1-2), it wasconfirmed that no hydroxyl group was present in a molecule.

To the trimethylolpropane-nonanoic acid ester (a1-2), lithium stearatewas added in an amount of not less than 10% by weight, and they wereheated to not lower than the melting point of lithium stearate to obtaina lithium soap grease. Then, to the lithium soap grease, thetrimethylolpropane-nonanoic acid ester (a1-2) was further added so thatthe penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 13.0mm, to prepare a lithium soap grease (A1-2).

(Lithium Soap Grease (A1-3))

Trimethylolpropane, decanoic acid and octanoic acid were mixed in amixing ratio of 1:2:2 (trimethylolpropane:decanoic acid:octanoic acid)by mol to perform esterification reaction, whereby a crudetrimethylolpropane-decanoic acid/octanoic acid mixed ester was obtained.From the crude trimethylolpropane-decanoic acid/octanoic acid mixedester, a trimethylolpropane-decanoic acid/octanoic acid mixed ester(a1-3) having no hydroxyl group in a molecule was separated by the useof Wakogel (available from Wako Pure Chemical Ind., Ltd.). By themeasurement of an infrared absorption spectrum of thetrimethylolpropane-decanoic acid/octanoic acid mixed ester (a1-3), itwas confirmed that no hydroxyl group was present in a molecule.

To the trimethylolpropane-decanoic acid/octanoic acid mixed ester(a1-3), lithium stearate was added in an amount of not less than 10% byweight, and they were heated to not lower than the melting point oflithium stearate to obtain a lithium soap grease. Then, to the lithiumsoap grease, the trimethylolpropane-decanoic acid/octanoic acid mixedester (a1-3) was further added so that the penetration (25° C.) of¼-cone (JIS K2220) for 0.1 seconds was 20.2 mm, to prepare a lithiumsoap grease (A1-3).

(Lithium Soap Grease (A1-4))

Trimethylolpropane and valeric acid were mixed in a mixing ratio of 1:2(trimethylolpropane:valeric acid) by mol to perform esterificationreaction, whereby a crude trimethylolpropane-valeric acid ester wasobtained. From the crude trimethylolpropane-valeric acid ester, atrimethylolpropane-valeric acid ester (a1-4) having no hydroxyl group ina molecule was separated by the use of Wakogel (available from Wako PureChemical Ind., Ltd.). By the measurement of an infrared absorptionspectrum of the trimethylolpropane-valeric acid ester (a1-4), it wasconfirmed that one hydroxyl group on the average was present in amolecule.

To the trimethylolpropane-valeric acid ester (a1-4), lithium stearatewas added in an amount of not less than 10% by weight, and they wereheated to not lower than the melting point of lithium stearate to obtaina lithium soap grease. Then, to the lithium soap grease, thetrimethylolpropane-valeric acid ester (a1-4) was further added so.thatthe penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 14.0mm, to prepare a lithium soap grease (A1-4).

(Urea Grease (A1-5))

Neopentyl glycol, decanoic acid and octanoic acid were mixed in a mixingratio of 1:3:3 (neopentyl glycol:decanoic acid:octanoic acid) by mol toperform esterification reaction, whereby a crude neopenytlglycol-decanoic acid/octanoic acid mixed ester was obtained. From thecrude neopentyl glycol-decanoic acid/octanoic acid mixed ester, anopentyl glycol-decanoic acid/octanoic acid mixed ester (a1-5) having nohydroxyl group in a molecule was separated by the use of Wakogel(available from Wako Pure Chemical Ind., Ltd.). By the measurement of aninfrared absorption spectrum of the neopentyl glycol-decanoicacid/octanoic acid mixed ester (a1-5), it was confirmed that no hydroxylgroup was present in a molecule.

To the neopentyl glycol-decanoic acid/octanoic acid mixed ester (a1-5),a diurea compound (A) represented by the following formula was added inan amount of not less than 10% by weight, and they were heated to notlower than the melting point of the diurea compound (A) to obtain a ureagrease.

Then, to the urea grease, the neopentyl glycol-decanoic acid/octanoicacid mixed ester (a1-5) was further added so that the penetration (25°C.) of ¼-cone (JIS K2220) for 0.1 seconds was 18.3 mm, to prepare a ureagrease (A1-5) The urea grease (A1-5) was held at 90° C. for 1000 hours.After that, a change in weight (evaporation loss) of the urea grease(A1-5) was measured, and as a result, the evaporation loss was 0.05% byweight.

(Urea Grease (A1-6))

Trimethylolpropane and decanoic acid were mixed in a mixing ratio of 1:4(trimethylolpropane:decanoic acid) by mol to perform esterificationreaction, whereby a crude trimethylolpropane-decanoic acid ester wasobtained. From the crude trimethylolpropane-decanoic acid ester, atrimethylolpropane-decanoic acid ester (a1-6) having no hydroxyl groupin a molecule was separated by the use of Wakogel (available from WakoPure Chemical Ind., Ltd.). By the measurement of an infrared absorptionspectrum of the trimethylolpropane-decanoic acid ester (a1-6), it wasconfirmed that no hydroxyl group was present in a molecule.

To the trimethylolpropane-decanoic acid ester (a1-6), a diurea compound(B) represented by the following formula was added in an amount of notless than 10% by weight, and they were heated to not lower than themelting point of the diurea compound (B) to obtain a urea grease.

Then, to the urea grease, the trimethylolpropane-decanoic acid/octanoicacid mixed ester (a1-5) was further added so that the penetration (25°C.) of ¼-cone (JIS K2220) for 0.1 seconds was 16.1 mm, to prepare a ureagrease (A1-6). The evaporation loss measured after the urea grease(A1-6) was held at 90° C. for 1000hours was 0.08% by weight.

(Urea Grease (A1-7))

To the trimethylolpropane-nonanoic acid ester (a1-2) having no hydroxylgroup in a molecule, the diurea compound (A) was added in an amount ofnot less than 10% by weight, and they were heated to not lower than themelting point of the diurea compound (A) to obtain a urea grease.

Then, to the urea grease, the trimethylolpropane-nonanoic acid ester(a1-2) was further added so that the penetration (25° C.) of ¼-cone (JISK2220) for 0.1 seconds was 15.5 mm, to prepare a urea grease (A1-7). Theevaporation loss measured after the urea grease (A1-7) was held at 90°C. for 1000 hours was 0.10% by weight.

Example 1

To the lithium soap grease (A1-1), trioleyl phosphate was added as ananti-wear agent in an amount of 1% by weight to prepare a lithium soapgrease composition. The lithium soap grease composition was stored in anatmosphere of a temperature of 40° C. and a humidity of 95% for 1000hours. Then, a percentage of moisture absorption of the lithium soapgrease composition was measured.

Using the lithium soap grease composition, a watch movement (CitizenWatch #2035, train wheel portion: made of metal (mainly made of brassand iron)) was assembled. Then, corrosion of the sliding mechanism ofthe slide portion was examined. The results are set forth in Table 1.

Comparative Example 1

A lithium soap grease composition was prepared in the same manner as inExample 1, except that the lithium soap grease (A1-4) was used insteadof the lithium soap grease (A1-1). Then a percentage of moistureabsorption of the lithium soap grease composition was measured in thesame manner as in Example 1.

For the lithium soap grease composition, corrosion of the slidingmechanism of the slide portion was examined in the same manner as inExample 1. The results are set forth in Table 1. TABLE 1 Percentage ofGrease moisture absorption Corrosion Lithium soap grease (A-1) 0.1% byweight not corroded Lithium soap grease (A-4) 8.9% by weight tarnished

Example 2

To the urea grease (A1-5), anti-wear agents shown in Table 2 were eachadded in an amount of every 0.05% by weight within the range of 0.1 to30% by weight to prepare urea grease compositions. Using the urea greasecompositions, watch movements (Citizen Watch #2035, train wheel portion:made of metal (mainly made of brass and iron)) were assembled. Then,operation confirmation test was carried out in the following manner. Theresults are set forth in Table 2.

(Operation Confirmation Test)

A crown was pulled to cause the watch to be in a state of adjustingtime. The crown was rotated in the time-advancing direction and-thetime-returning direction alternately to make time-adjusting operationscorresponding to those of a total of 10 years. Then, a ratio of thetorque measured after the time-adjusting operations to the torquemeasured before the time-adjusting operations, namely, torque decreaseratio, was determined.

Comparative Example 2

Urea grease compositions were prepared in the same manner as in Example2, except that the anti-wear agents shown in Table 2 were each added inan amount of 0% by weight or 0.05% by weight to the urea grease (A1-5).Using the urea grease compositions, watch movements were assembled andoperation confirmation tests of the watch movements were carried out, inthe same manner as in Example 2. The results are set forth in Table 2.TABLE 2 Amount Torque added decrease Overall Anti-wear agent (wt %)Corrosion ratio judgment Zinc 0 — C C diethyldithiophosphate 0.05 B C C0.1˜30 B A B Distearyl sulfide 0 — C C 0.05 B C C 0.1˜30 B A B Tricresylphosphate 0 — C C 0.05 A C C 0.1˜30 A A A Lauryl acid phosphate 0 — C C0.05 A C C 0.1˜30 B A B Trioleyl phosphite 0 — C C 0.05 A C C 0.1˜30 A AA Dilauryl 0 — C C hydrogenphosphite 0.05 A C C 0.1˜30 B A B Lauryl acidphosphate 0 — C C diethylamine salt 0.05 A C C 0.1˜30 B A B Calciumborate 0 — C C 0.05 A C C 0.1˜30 A A A(Evaluation)Corrosion:A: The metal part was free from corrosion, change of appearance andchange of properties.B: The metal part was a little corroded.C: The metal part was markedly corroded.Torque decrease ratio:A: The torque decrease ratio was in the range of about 10 to 15%.B: The torque decrease ratio was more than 15%.C: A marked decrease was found in the initial stage of the operationconfirmation test.Overall judgment:A: The watch movement is employable for a long period of time.B: The watch movement is employable for a short period of time.C: The watch movement is difficult to use.

According to Table 2, when the amount of the anti-wear agent added wasless than 0.1% by weight, marked decrease of torque was found in any ofthe anti-wear agents in the initial stage of the operation confirmationtest. Further, as the amount of the anti-wear agent added was increased,the torque decrease ratio was lowered, but when the amount thereofexceeded 20% by weight, the torque decrease ratio was almost constant atabout 10%. Hence, it has been confirmed that taking economicalefficiency into consideration, the amount of the anti-wear agent addedis preferably in the range of 0.1 to 20% by weight.

Example 3

To the lithium soap grease (A1-2), trixylenyl phosphate was.added as ananti-wear agent in an amount of 2% by weight to prepare a lithium soapgrease composition. Separately, to the lithium soap grease composition,PTFE particles (particle diameter: 0.5 to 8 μm) or molybdenum disulfidewas added as a solid lubricant in an amount of every 0.05% by weightwithin the range of 0.01 to 10% by weight to prepare lithium soap greasecompositions containing a solid lubricant. Using the lithium soap greasecompositions, watch movements were assembled and operation confirmationtests of the watch movements were carried out, in the same manner as inExample 2. The results are set forth in Table 3. TABLE 3 Torque Amountadded decrease Solid lubricant (wt %) ratio PTFE particle 0 9.5% 0.01˜109˜5%  Molybdenum disulfide 0 9.5% 0.01˜10 9˜5% 

With increase of the amount of the solid lubricant added, the torquedecrease ratio was lowered, but when the amount thereof exceeded 5% byweight, the torque decrease ratio was almost constant at about 5%.Hence, it has been confirmed that taking economical efficiency intoconsideration, the amount of the anti-wear agent added is preferably inthe range of 0.01 to 5% by weight.

Example 4

To the lithium soap grease (A1-3), trioleyl phosphite was added as ananti-wear agent in an amount of 5% by weight to prepare a lithium soapgrease composition. Separately, to the lithium soap grease composition,0.05% by weight of benzotriazole as a metal deactivator and 0.05% byweight of a diphenylamine derivative as an antioxidant were added toprepare a lithium soap grease composition containing a metal deactivatorand an antioxidant. Using the lithium soap grease compositions, watchmovements were assembled in the same manner as in Example 2. Then,operation confirmation test was carried out in the same manner as inExample 2, except that high-temperature operation confirmation test at80° C. was added. The results are set forth in Table 4. TABLE 4Benzotriazole 0 wt % 0.05 wt % Diphenylamine derivative 0 wt % 0.05 wt %Torque decrease ratio Ordinary temperature  7.5% 7.5% 80° C. 32.4% 9.5%Corrosion Ordinary temperature not corroded not corroded 80° C. corrodednot corroded

Example 5

To each of the urea greases (A1-5) to (A1-7), tristearyl phosphate wasadded as an anti-wear agent in an amount of 5% by weight to prepare ureagrease compositions. Using the urea grease compositions, watch movementswere assembled in the same manner as in Example 2. The watch movementswere stored. at a high temperature of 80° C. Then, operationconfirmation test was carried out in the same manner as in Example 2.The results are set forth in Table 5. TABLE 5 Evaporation loss Torque(after stored at 90° C. decrease Urea grease for 1000 hrs) ratio Ureagrease (A1-5) 0.05 wt % 4.5% Urea grease (A1-6) 0.08 wt % 5.0% Ureagrease (A1-7) 0.10 wt % 4.8%

Example 6

To the lithium soap grease (A1-3), trioleyl phosphite was added as ananti-wear agent in an amount of 5% by weight to prepare lithium soapgrease compositions. The lithium soap grease compositions had total acidnumbers of 0.1 to 3 mgKQH/g. Separately, to each of the lithium soapgrease compositions, 0.05% by weight of benzotriazole as a metaldeactivator and 0.05% by weight of a diphenylamine derivative as anantioxidant were added to prepare lithium soap grease compositionscontaining a metal deactivator and an antioxidant.

Using the lithium soap grease compositions, watch movements wereassembled and operation confirmation tests of the watch movements werecarried out, in the same manner as in Example 2. The results are setforth in Table 6. TABLE 6 Appearance of metal part Total acid in theinitial stage number of operation After operation Overall (mgKOH/g)confirmation test confirmation test judgment 0 to 0.2 AcceptableAcceptable A more than 0.2 Acceptable Corroded and tarnish B(Evaluation)Overall judgment:A: The watch movement is employable for a long period of time.B: The watch movement is employable for a short period of time.C: The watch movement is difficult to use.<Preparation of Grease (A2)>

Greases (A2) used in Examples 7 to 12 and Comparative Example 3 aregiven below.

(Lithium Soap Grease (A2-1))

To trimer of 1-decene, lithium stearate was added in an amount of notless than 10% by weight, and they were heated to not lower than themelting point of lithium stearate to obtain a lithium soap grease. Then,to the lithium soap grease, the trimer of 1-decene was further added sothat the penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was15.0 mm, to prepare a lithium soap grease (A2-1).

(Lithium Soap Grease (A2-2))

To tetramer of 1-decene, lithium stearate was added in an amount of notless than 10% by weight, and they were heated to not lower than themelting point of lithium stearate to obtain a lithium soap grease. Then,to the lithium soap grease, the tetramer of 1-decene was further addedso that the penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 secondswas 20.5 mm, to prepare a lithium soap grease (A2-2).

(Lithium Soap Grease (A2-3))

To trimer of 1-undecene, lithium stearate was added in an amount of notless than 10% by weight, and they were heated to not lower than themelting point of lithium stearate to obtain a lithium soap grease. Then,to the lithium soap grease, the trimer of 1-undecene was further addedso that the penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 secondswas 15.8 mm, to prepare a lithium soap grease (A2-3).

(Lithium Soap Grease (A2-4))

To trimer of 1-dodecene, lithium stearate was added in an amount of notless than 10% by weight, and they were heated to not lower than themelting point of lithium stearate to obtain a lithium soap grease. Then,to the lithium soap grease, the trimer of 1-dodecene was further addedso that the penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 secondswas 17.5 mm, to prepare a lithium soap grease (A2-4).

(Urea Grease (A2-5))

To trimer of 1-decene, the diurea compound (A) was added in an amount ofnot less than 10% by weight, and they were heated to not lower than themelting point of the diurea compound (A) to obtain a urea grease. Then,to the urea grease, the trimer of 1-decene was further added so that thepenetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 21.1 mm,to prepare a urea grease (A2-5). The evaporation loss measured after theurea grease (A2-5) was held at 90° C. for 1000 hours was 0.07% byweight.

(Urea Grease (A2-6))

To trimer of 1-decene, the diurea compound (B) was added in an amount ofnot less than 10% by weight, and they were heated to not lower than themelting point of the diurea compound (B) to obtain a urea grease. Then,to the urea grease, the trimer of 1-decene was further added so that thepenetration (25° C.) of ¼-cone (JIS K2220) for 0.1seconds was 17.5 mm,to prepare a urea grease (A2-6). The evaporation loss measured after theurea grease (A2-6) was held at 90° C. for 1000 hours was 0.06% byweight.

(Urea Grease (A2-7))

To trimer of 1-undecene, a diurea compound (C) represented by thefollowing formula was added in an amount of not less than 10% by weight,and they were heated to not lower than the melting point of the diureacompound (C) to obtain a urea grease.

Then, to the urea grease, the trimer of 1-decene was further added sothat the penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was14.5 mm, to prepare a urea grease (A2-7). The evaporation loss measuredafter the urea grease (A2-7) was held at 90° C. for 1000 hours was 0.07%by weight.

Example 7

To each of the lithium soap greases (A2-1) and (A2-2), trioleylphosphate was added as an anti-wear agent in an amount. of 1% by weightto prepare lithium soap grease compositions. Using the lithium soapgrease compositions, watch movements were assembled in the same manneras in Example 2. The watch movements were stored at a high temperatureof 80° C. Then, operation confirmation test was carried out in the samemanner as in Example 2. The results are set forth in Table 7. TABLE 7Torque Number of carbon decrease Grease in hydrocarbon oil ratio Lithiumsoap grease (A2-1) 30 10.8% Lithium soap grease (A2-2) 40 10.2%

Example 8

To the urea grease (A2-5), anti-wear agents shown in Table 8 were eachadded in an amount of every 0.05% by weight within the range of 0.1 to30% by weight to prepare urea grease compositions. Using the urea greasecompositions, watch movements were assembled and operation confirmationtests of the watch movements were carried out, in the same manner as inExample 2. The results are set forth in Table 8.

Comparative Example 3

Urea grease compositions were prepared in the same manner as in Example8, except that the anti-wear agents shown in Table 8 were each added inan amount of 0% by weight or 0.05% by weight to the urea grease (A2-5).Using the urea grease compositions, watch movements were assembled andoperation confirmation tests of the watch movements were carried out, inthe same manner as in Example 8. The results are set forth in Table 8.TABLE 8 Amount Torque added decrease Overall Anti-wear agent (wt %)Corrosion ratio judgment Zinc 0 — C C diethyldithiophosphate 0.05 B C C0.1˜30 B A B Distearyl sulfide 0 — C C 0.05 B C C 0.1˜30 B A B Tricresylphosphate 0 — C C 0.05 A C C 0.1˜30 A A A Lauryl acid phosphate 0 — C C0.05 A C C 0.1˜30 B A B Trioleyl phosphite 0 — C C 0.05 A C C 0.1˜30 A AA Dilauryl 0 — C C hydrogenphosphite 0.05 A C C 0.1˜30 B A B Lauryl acidphosphate 0 — C C diethylamine salt 0.05 A C C 0.1˜30 B A B Calciumborate 0 — C C 0.05 A C C 0.1˜30 A A A(Evaluation)Corrosion:A: The metal part was free from corrosion, change of appearance andchange of properties.B: The metal part was a little corroded.C: The metal part was markedly corroded.Torque decrease ratio:A: The torque decrease ratio was in the range of about 10 to 15%.B: The torque decrease ratio was more than 15%.C: A marked decrease was found in the initial stage of the operationconfirmation test.Overall judgment:A: The watch movement is employable for a long period of time.B: The watch movement is employable for a short period of time.C: The watch movement is difficult to use.

According to Table 8, when the amount of the anti-wear agent added wasless than 0.1% by weight, marked decrease of torque was found in any ofthe anti-wear agents in the initial stage of the operation confirmationtest. Further, as the amount of the anti-wear agent added was increased,the torque decrease ratio was lowered, but when the amount thereofexceeded 20% by weight, the torque decrease ratio was almost constant atabout 10%. Hence, it has been confirmed that taking economicalefficiency into consideration, the amount of the anti-wear agent addedis preferably in the range of 0.1 to 20% by weight.

Example 9

To the lithium soap grease (A2-3), trixylenyl phosphate was added as ananti-wear agent in an amount of 2% by weight to prepare a lithium soapgrease composition. Separately, to the lithium soap grease composition,PTFE particles (particle diameter: 0.5 to 8 μm) or molybdenum disulfidewas added as a solid lubricant in an amount of every 0.05% by weightwithin the range of 0.01 to 10% by weight to prepare lithium soap greasecompositions containing a solid lubricant. Using the lithium soap greasecompositions, watch movements were assembled and operation confirmationtests of the watch movements were carried out, in the same manner as inExample 2. The results are set forth in Table9. TABLE 9 Torque Amountadded decrease Solid lubricant (wt %) ratio PTFE particle 0  9.7%0.01˜10 9˜5% Molybdenum disulfide 0  10.0%  0.01˜10 9˜5%

With increase of the amount of the solid lubricant added, the torquedecrease ratio was lowered, but when the amount thereof exceeded 5% byweight, the torque decrease ratio was almost constant at about 5%.Hence, it has been confirmed that taking economical efficiency intoconsideration, the amount of the anti-wear agent added is preferably inthe range of 0.01 to 5% by weight.

Example 10

To the lithium soap. grease (A2-4), trioleyl phosphite was added as ananti-wear agent in an amount of 5% by weight to prepare a lithium soapgrease composition. Separately, to the lithium soap grease composition,0.05% by weight of benzotriazole as a metal deactivator and 0.05% byweight of a diphenylamine derivative as an antioxidant were added toprepare a lithium soap grease composition containing a metal deactivatorand an antioxidant. Using the lithium soap grease compositions, watchmovements were assembled in the same manner as in Example 2. Then,operation confirmation test was carried out in the same manner as inExample 2, except that high-temperature operation confirmation test at80° C. was added. The results are set forth in Table 10. TABLE 10Benzotriazole 0 wt % 0.05 wt % Diphenylamine derivative 0 wt % 0.05 wt %Torque decrease ratio Ordinary temperature  7.5% 6.5% 80° C. 35.8% 8.9%Corrosion Ordinary temperature not corroded not corroded 80° C. corrodednot corroded

Example 11

To each of the urea greases (A2-5) to (A2-7), tristearyl phosphate wasadded as an anti-wear agent in an amount of 5% by weight to prepare ureagrease compositions. Using the urea grease compositions, watch movementswere assembled in the same manner as in Example 2. The watch 15movements were stored at a high temperature of 80° C. Then, operationconfirmation test was carried out in the same manner as in Example 2.The results are set forth in Table 11 TABLE 11 Evaporation loss Torque(after stored at 90° C. decrease Urea grease for 1000 hrs) ratio Ureagrease (A2-5) 0.07 wt % 9.5% Urea grease (A2-6) 0.06 wt % 12.1% Ureagrease (A2-7) 0.07 wt % 11.3%

Example 12

To the lithium soap grease (A2-3), trioleyl phosphite was added as ananti-wear agent in an amount of 5% by weight to prepare lithium soapgrease compositions. The lithium soap grease compositions had total acidnumbers of 0.1 to 3 mgKOH/g. Separately, to each of the lithium soapgrease compositions, 0.05% by weight of benzotriazole as a metaldeactivator and 0.05% by weight of a diphenylamine derivative as anantioxidant were added to prepare lithium soap grease compositionscontaining a metal deactivator and an antioxidant.

Using the lithium soap grease compositions, watch movements wereassembled and operation confirmation tests of the watch movements werecarried out, in the same manner as in Example 2. The results are setforth in Table 12. TABLE 12 Appearance of metal part Total acid in theinitial stage number of operation After operation Overall (mgKOH/g)confirmation test confirmation test judgment 0 to 0.2 AcceptableAcceptable A more than 0.2 Acceptable Corroded and tarnish B(Evaluation)Overall judgment:A: The watch movement is employable for a long period of time.B: The watch movement is employable for a short period of time.C: The watch movement is difficult to use.<Preparation of Grease (A3)>

Greases (A3) used in Examples 13 to 18 and Comparative Examples 4 to 5are given below.

(Lithium Soap Grease (A3-1))

To an ether oil (a3-1) represented by the following formula,C₁₀H₂₁O—CH₂CH₂₃C₁₀H₂₁lithium stearate was added in an amount of not less than 10% by weight,and they were heated to not lower than the melting point of lithiumstearate to obtain a lithium soap grease. Then, to the lithium soapgrease, the ether oil (a3-1) was further added so that the penetration(25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 15.2 mm, to prepare alithium soap grease (A3-1).(Lithium Soap Grease (A3-2))

To an ether oil (a3-2) represented by the following formula,C₁₀H₂₁O—CH₂CH₂₃OHlithium stearate was added in an amount of not less than 10% by weight,and they were heated to not lower than the melting point of lithiumstearate to obtain a lithium soap grease. Then, to the lithium soapgrease, the ether oil (a3-2) was further added so that the penetration(25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 17.1 mm, to prepare alithium soap grease (A3-2).(Urea Grease (A3-3))

To an ether oil (a3-3) represented by the following formula,C₆H₁₃O—CH₂₃C₆H₁₃a diurea compound (D) represented by the following formula was added inan amount of not less than 10% by weight, and they were heated to notlower than the melting point of the diurea compound (D) to obtain a ureagrease.

Then, to the urea grease, the ether oil (a3-3) was further added so thatthe penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 15.5mm, to prepare a urea grease (A3-3). The evaporation loss measured afterthe urea grease (A3-3) was held at 90° C. for 1000 hours was 0.05% byweight.

(Urea Grease (A3-4))

To an ether oil (a3-4) represented by the following formula,C₇H₁₅—O—C₂H₄—C₇H₁₅a diurea compound (E) represented by the following formula was added inan amount of not less than 10% by weight, and they were heated to notlower than the melting point of the diurea compound (E) to obtain a ureagrease.

Then, to the urea grease, the ether oil (a3-4) was further added so thatthe penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 15.8mm, to prepare a urea grease (A3-4). The evaporation-loss measured afterthe urea grease (A3-4) was held at 90° C. for 1000 hours was 0.11% byweight.

(Urea Grease (A3-5))

To an ether oil (a3-5) represented by the following formula,

the diurea compound (A) was added in an amount of not less than 10% byweight, and they were heated to not lower than the melting point of thediurea compound (A) to obtain a urea grease.

Then, to the urea grease, the ether oil (a3-5) was further added so thatthe penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was 20.1mm, to prepare a urea grease (A3-5). The evaporation loss measured afterthe urea grease (A3-5) was held at 90° C. for 1000 hours was 0.11% byweight.

Example 13

To the lithium soap grease (A3-1), trioleyl phosphate was added as ananti-wear agent in an amount of 1% by weight to prepare a lithium soapgrease composition. The lithium soap grease composition was stored in anatmosphere of a temperature of 40° C. and a humidity of 95% for 1000hours. Then, a percentage of moisture absorption of the lithium soapgrease composition was measured.

Using the lithium soap grease composition, a watch movement (CitizenWatch #2035, train wheel portion: made of metal (mainly made of brassand iron)) was assembled. Then, corrosion of the sliding mechanism ofthe slide portion was examined. The results are set forth in Table 13.

Comparative Example 4

A lithium soap grease composition was prepared in the same manner as inExample 1, except that the lithium soap grease (A3-2) was used insteadof the lithium soap grease (A3-1). Then a percentage of moistureabsorption of the lithium soap grease composition was measured in thesame manner as in Example 13.

For the lithium soap grease composition, corrosion of the slidingmechanism of the slide portion was examined in the same manner as inExample 13. The results are set forth in Table 13. TABLE 13 Percentageof Grease moisture absorption Corrosion Lithium soap grease (A-1) 0.3%by weight not corroded Lithium soap grease (A-4) 7.8% by weighttarnished

Example 14

To the urea grease (A3-3), anti-wear agents shown in Table 14 were eachadded in an amount of every 0.05% by weight within the range of 0.1 to30% by weight to prepare urea grease compositions. Using the urea greasecompositions, watch movements were assembled and operation confirmationtests of the watch movements were carried out, in the same manner as inExample 2. The results are set forth in Table 14.

Comparative Example 5

Urea grease compositions were prepared in the same manner as in Example14, except that the anti-wear agents shown in Table 14 were each addedin an amount of 0% by weight or 0.05% by weight to the urea grease(A3-3). Using the urea grease compositions, watch movements wereassembled and operation confirmation tests of the watch movements werecarried out, in the same manner as in Example 14. The results are setforth in Table 14. TABLE 14 Amount Torque added decrease OverallAnti-wear agent (wt %) Corrosion ratio judgment Zinc 0 — C Cdiethyldithiophosphate 0.05 B C C 0.1˜30 B A B Distearyl sulfide 0 — C C0.05 B C C 0.1˜30 B A B Tricresyl phosphate 0 — C C 0.05 A C C 0.1˜30 AA A Lauryl acid phosphate 0 — C C 0.05 A C C 0.1˜30 B A B Trioleylphosphite 0 — C C 0.05 A C C 0.1˜30 A A A Dilauryl 0 — C Chydrogenphosphite 0.05 A C C 0.1˜30 B A B Lauryl acid phosphate 0 — C Cdiethylamine salt 0.05 A C C 0.1˜30 B A B Calcium borate 0 — C C 0.05 AC C 0.1˜30 A A A(Evaluation)Corrosion:A: The metal part was free from corrosion, change of appearance andchange of properties.B: The metal part was a little corroded.C: The metal part was markedly corroded.Torque decrease ratio:A: The torque decrease ratio was in the range of about 10 to 15%.B: The torque decrease ratio was more than 15%.C: A marked decrease was found in the initial stage of the operationconfirmation test.Overall judgment:A: The watch movement is employable for a long period of time.B: The watch movement is employable for a short period of time.C: The watch movement is difficult to use.

According to Table 14, when the amount of the anti-wear agent added wasless than 0.1% by weight, marked decrease of torque was found in any ofthe anti-wear agents in the initial stage of the operation confirmationtest. Further, as the amount of the anti-wear agent added was increased,the torque decrease ratio was lowered, but when the amount thereofexceeded 20% by weight, the torque decrease ratio was almost constant atabout 10%. Hence, it has been confirmed that taking economicalefficiency into consideration, the amount of the anti-wear agent addedis preferably in the range of 0.1 to 20% by weight.

Example 15

To the lithium soap grease (A3-1), trixylenyl phosphate was added as ananti-wear agent in an amount of 2% by weight to prepare a lithium soapgrease composition. Separately, to the lithium soap grease composition,PTFE particles (particle diameter: 0.5 to 8 μm) or molybdenum disulfidewas added as a solid lubricant in an amount of every 0.05% by weightwithin the range of 0.01 to 10% by weight to prepare lithium soap greasecompositions containing a solid lubricant. Using the lithium soap greasecompositions, watch movements were assembled and operation confirmationtests of the watch movements were carried out, in the same manner as inExample 2. The results are set forth in Table 15. TABLE 15 Torque Amountadded decrease Solid lubricant (wt %) ratio PTFE particle 0 10.3%0.01˜10  9˜5%  Molybdenum disulfide 0 10.3% 0.01˜10  9˜5% 

With increase of the amount of the solid lubricant added, the torquedecrease ratio was lowered, but when the amount thereof exceeded 5% byweight, the torque decrease ratio was almost constant at about 5%.Hence, it has been confirmed that taking economical efficiency intoconsideration, the amount of the anti-wear agent added is preferably inthe range of 0.01 to 5% by weight.

Example 16

To the lithium soap grease (A3-1), trioleyl phosphite was added as ananti-wear agent in an amount of 5% by weight to prepare a lithium soapgrease composition. Separately, to the lithium soap grease composition,0.05% by weight of benzotriazole as a metal deactivator and 0.05% byweight of a diphenylamine derivative as an antioxidant were added toprepare a lithium soap grease composition containing a metal deactivatorand an antioxidant. Using the lithium soap grease compositions, watchmovements were assembled in the same manner as in Example 2. Then,operation confirmation test was carried out in the same manner as inExample 2, except that high-temperature operation confirmation test at80° C. was added. The results are set forth in Table 16. TABLE 16Benzotriazole 0 wt % 0.05 wt % Diphenylamine derivative 0 wt % 0.05 wt %Torque decrease ratio • Ordinary temperature  7.3% 7.0% 80° C. 35.4%9.7% Corrosion Ordinary temperature not corroded not corroded 80° C.corroded not corroded

Example 17

To each of the urea greases (A3-3) to (A3-5), tristearyl phosphate wasadded as an anti-wear agent in an amount of 5% by weight to prepare ureagrease compositions. Using the urea grease compositions, watch movementswere assembled in the same manner as in Example 2. The watch movementswere stored at a high temperature of 80° C. Then, operation confirmationtest was carried out in the same manner as in Example 2. The results areset forth in Table 17. TABLE 17 Evaporation loss Torque (after stored at90° C. decrease Urea grease for 1000 hrs) ratio Urea grease (A3-3) 0.05wt % 9.4% Urea grease (A3-4) 0.11 wt % 11.1% Urea grease (A3-5) 0.11 wt% 10.8%

Example 18

To the lithium soap grease (A3-1), trioleyl phosphite was added as ananti-wear agent in an amount of 5% by weight to prepare lithium soapgrease compositions. The lithium soap grease compositions had total acidnumbers of 0.1 to 3 mgKOH/g. Separately, to each of the lithium soapgrease compositions, 0.05% by weight of benzotriazole as a metaldeactivator and 0.05% by weight of a diphenylamine derivative as anantioxidant were added to prepare lithium soap grease compositionscontaining a metal deactivator and an antioxidant.

Using the lithium soap grease compositions, watch movements wereassembled and operation confirmation tests of the watch movements werecarried out, in the same manner as in Example 2. The results are setforth in Table 18. TABLE 18 Appearance of metal part Total acid in theinitial stage number of operation After operation Overall (mgKOH/g)confirmation test confirmation test judgment 0 to 0.2 AcceptableAcceptable A more than 0.2 Acceptable Corroded and tarnish B(Evaluation)Overall judgment:A: The watch movement is employable for a long period of time.B: The watch movement is employable for a short period of time.C: The watch movement is difficult to use.

Example 19

To each of ether oils, lithium stearate was added in an amount of notless than 10% by weight, and they were heated to not lower than themelting point of lithium stearate to obtain lithium soap greases. Then,to each of the lithium soap greases, the ether oil was further added sothat the penetration (25° C.) of ¼-cone (JIS K2220) for 0.1 seconds was18.4 mm, to prepare lithium soap greases. The ether oil used in thisExample is represented by the following formula:R₁O—R₂_(n)R₃wherein R₁ and R₃ are each independently an alkyl group of 1 to 18carbon atoms or a monovalent aromatic hydrocarbon group of 6 to 18carbon atoms, R₂ is an alkylene group of 1 to 18 carbon atoms or adivalent aromatic hydrocarbon group of 6 to 18 carbon atoms, and n is aninteger of 1 to 5.

To each of the lithium soap greases, trioleyl phosphate was added as ananti-wear agent in an amount of 1% by weight to prepare lithium soapgrease compositions. Using the lithium soap grease compositions, watchmovements were assembled in the same manner as in Example 2. The watchmovements were stored at a high temperature of 80° C. Then, operationconfirmation test was carried out in the same manner as in Example 2. Asa result, in any of the grease compositions, torque decrease ratios wereabout 10 to 15%, and the watch was favorably operated.

Example 20

Lubricating oil compositions and grease compositions used in thisExample are given below.

(Polyol Ester Type Lubricating Oil Composition)

To the trimethylolpropane-valeric acid ester (a1-1), 2% by weight ofpolymethylmethacrylate (available from Sanyo Chemical Ind., Ltd., tradename: ACLUBE) as a viscosity index improver and 5% by weight of trioleylphosphate as an anti-wear agent was added to prepare a lubricating oilcomposition containing a polyol ester.

(Hydrocarbon Type Lubricating Oil Composition)

To a trimer of 1-decene, 3% by weight of polyolefin (available fromMitsui Chemicals, Inc., trade name: LUCANT) as a viscosity indeximprover and 5% by weight of trioleyl phosphate as an anti-wear agentwas added to prepare a lubricating oil composition containing ahydrocarbon.

(Ether Type Lubricating Oil Composition)

To the ether oil (a3-1), 2.5% by weight of polymethylmethacrylate(available from Sanyo Chemical Ind., Ltd., trade name: ACLUBE) as aviscosity index improver and 5% by weight of trioleyl phosphate as ananti-wear agent was added to prepare a lubricating oil compositioncontaining an ether oil.

(Polyol Ester Type Grease Composition)

To the lithium soap grease (A1-1), trioleyl phosphate was added as ananti-wear agent in an amount of 1% by weight to prepare a polyol estertype grease composition.

(Hydrocarbon Type Grease Composition)

To the lithium soap grease (A2-1), trioleyl phosphate was added as ananti-wear agent in an amount of 1% by weight to prepare a hydrocarbontype grease composition.

(Ether Type Grease Composition)

To the lithium soap grease (A3-1), trioleyl phosphate was added as ananti-wear agent in an amount of 1% by weight to prepare an ether typegrease composition.

(Assembly of Watch)

Each of the grease compositions was applied to a sliding mechanism of aslide portion in watch movements (Citizen Watch #2035, train wheelportion: made of metal (mainly made of brass and iron)). Each of thelubricating compositions was applied to a slide portion other than thesliding mechanism. Then, watches were assembled the watch movements.

A crown was pulled to cause the watch to be in a state of adjustingtime. The crown was continuously rotated for 2 hours. The results areset forth in Table 19. TABLE 19 Lubricating oil composition Polyol esterHydrocarbon type type Ether type Grease Polyol ester A B B compositiontype Hydrocarbon B A B type Ether type B B A(Evaluation)Overall judgment:A: Properties of the lubricating oil composition was not change.B: Properties of the lubricating oil composition was a little change,but an operating performance of the watch was acceptable.C: Properties of the lubricating oil composition was change, and anoperating performance of the watch was not acceptable.

Example 21

To lithium soap grease (A2-3), trixylenyl phosphate was added as ananti-wear agent in an amount of 2% by weight to prepare a lithium soapgrease composition. Separately, to the lithium soap grease composition,PTFE particles (particle diameter: 0.5 to 8 μm) was added as a solidlubricant in an amount of 3% by weight to prepare lithium soap greasecomposition containing a solid lubricant.

Using the lithium soap grease compositions containing a solid lubricant,a watch movement (Citizen Watch #2035, train wheel portion: made ofmetal (mainly made of brass and iron)) was assembled. A crown was pulledto cause the watch to be in a state of adjusting time. The crown wascontinuously rotated for 2 hours, and a slip torque was measured.

Thereafter, the watch was disassembled and washed, and the watch wasre-assembled using as a grease composition the lithium soap greasecomposition containing no solid lubricant. A crown was pulled to causethe watch to be in a state of adjusting time. The crown was continuouslyrotated for 2 hours, and a slip torque was measured.

The slip torque decrease ratio of the watch are set forth in Table 20.

Comparative Example 6

A slip torque was measured in the same manner as in Example 21, exceptthat the lithium soap grease composition containing no solid lubricantwas used as both of a grease compositions. TABLE 20 Torque decrease Ex.21 6.0% Comp. Ex. 6 19.8%

According to Table 20, in the watch which was first assembled using thegrease composition containing a solid lubricant, even when the watch wasdisassembled, washed and re-assembled using the grease compositioncontaining no solid lubricant, it has been confirmed that a decrease ofa slip torque is inhibited.

For the watches assembled using each of the polyol ester type greasecomposition and the ether type grease composition, the same results wereobtained.

INDUSTRIAL APPLICABILITY

By the use of the grease composition for a precision instrument of theinvention for a sliding mechanism of a precision instrument such as awatch, a stable slip torque can be obtained, and the precisioninstrument such as a watch can be stably operated. Further, by the useof the grease composition for a precision instrument of the inventionfor a sliding mechanism of a precision instrument such as a watch incombination with the same type of a lubricating oil composition as thegrease composition, properties of the lubricating oil are not changed,and the precision instrument such as a watch can be stably operated.

1. A grease composition for a precision instrument comprising a lithium soap grease or a urea grease, and an anti-wear agent: wherein the lithium soap grease and the urea grease are each a grease having no hydroxyl group in a molecule, and the anti-wear agent is contained in an amount of 0.1 to 20% by weight based on the total amount of the grease composition.
 2. The grease composition for a precision instrument as claimed in claim 1, wherein the lithium soap grease or the urea grease is obtained from a polyol ester oil having no hydroxyl group in a molecule.
 3. The grease composition for a precision instrument as claimed in claim 1, wherein the lithium soap grease or the urea grease is obtained from a paraffinic hydrocarbon oil comprising an α-olefin polymer of 30 or more carbon atoms.
 4. The grease composition for a precision instrument as claimed in claim 1, wherein the lithium soap grease or the urea grease is obtained from an ether oil having no hydroxyl group in a molecule.
 5. The grease composition for a precision instrument as claimed in claim 4, wherein the ether oil is an ether oil represented by the following formula (1): R₁O—R₂_(n)R₃  (1)wherein R₁ and R₃ are each independently an alkyl group of 1 to 18 carbon atoms or a monovalent aromatic hydrocarbon group of 6 to 18 carbon atoms, R₂ is an alkylene group of 1 to 18 carbon atoms or a divalent aromatic hydrocarbon group of 6 to 18 carbon atoms, and n is an integer of 1 to
 5. 6. The grease composition for a precision instrument as claimed in claim 1, wherein the anti-wear agent is at least one compound selected from a neutral phosphate, a neutral phosphite and calcium borate.
 7. The grease composition for a precision instrument as claimed in claim 1, further comprising a solid lubricant in an amount of 0.01 to 5% by weight based on the total amount of the grease composition.
 8. The grease composition for a precision instrument as claimed in claim 7, wherein the solid lubricant comprises molybdenum disulfide and/or PTFE particles.
 9. The grease composition for a precision instrument as claimed in claim 1, further comprising a metal deactivator.
 10. The grease composition for a precision instrument as claimed in claim 9, wherein the metal deactivator is benzotriazole and/or a derivative thereof.
 11. The grease composition for a precision instrument as claimed in claim 1, further comprising an antioxidant.
 12. The grease composition for a precision instrument as claimed in claim 11, wherein the antioxidant is a phenol type antioxidant and/or an amine type antioxidant.
 13. The grease composition for a precision instrument as claimed in claim 12, wherein the phenol type antioxidant is 2,6-di-tributyl-p-cresol, 2,4,6-tri-t-butylphenol or 4,4′-methylenebis(2,6-di-tributylphenol).
 14. The grease composition for a precision instrument as claimed in claim 12, wherein the amine type antioxidant is a diphenylamine derivative.
 15. The grease composition for a precision instrument as claimed in claim 1, wherein the change in weight of the lithium soap grease or the urea grease after the grease is held at 90° C. for 1000 hours is not more than 10% by weight.
 16. The grease composition for a precision instrument as claimed in claim 1, which has a total acid number of not more than 0.2 mgKOH/g.
 17. A watch, wherein the grease composition for a precision instrument of claim 1 is used for a sliding mechanism of its slide portion.
 18. The watch as claimed in claim 17, wherein a grease composition for a precision instrument is used for a sliding mechanism of a slide portion, a lubricating oil composition is used for portions other than the sliding mechanism of the slide portion, the grease composition is a grease composition obtained from a polyol ester oil having no hydroxyl group in a molecule, and the lubricating oil composition is a lubricating oil composition obtained from the polyol ester oil having no hydroxyl group in a molecule.
 19. The watch as claimed in claim 17, wherein a grease composition for a precision instrument is used for a sliding mechanism of a slide portion, a lubricating oil composition is used for portions other than the sliding mechanism of the slide portion, the grease composition is a grease composition obtained from a paraffinic hydrocarbon oil comprising an α-olefin polymer of 30 or more carbon atoms, and the lubricating oil composition is a lubricating oil composition obtained from the paraffinic hydrocarbon oil comprising an α-olefin polymer of 30 or more carbon atoms.
 20. The watch as claimed in claim 17, wherein a grease composition for a precision instrument is used for a sliding mechanism of a slide portion, a lubricating oil composition is used for portions other than the sliding mechanism of the slide portion, the grease composition is a grease composition obtained from an ether oil having no hydroxyl group in a molecule, and the lubricating oil composition is a lubricating oil composition obtained from the ether oil having no hydroxyl group in a molecule.
 21. A maintenance method of a watch in which a grease composition for a precision instrument containing a solid lubricant is used for a sliding mechanism of a slide portion, comprising: after disassembly and washing of the watch, re-assembling the watch using a grease composition for a precision instrument containing no solid lubricant in a sliding mechanism of a slide portion. 